正交晶系
声子
钙钛矿(结构)
材料科学
简并能级
密度泛函理论
凝聚态物理
八面体
无定形固体
卤化物
布里渊区
带隙
单斜晶系
从头算
从头算量子化学方法
结构稳定性
结晶学
晶体结构
化学
计算化学
分子
物理
无机化学
工程类
有机化学
结构工程
量子力学
标识
DOI:10.1021/acs.jpclett.2c02047
摘要
Halide perovskites have been intensively investigated for photovoltaic applications because of their good optoelectronic properties and low cost. Various high-pressure experiments have shown that these materials generally undergo reversible phase transitions between different crystalline phases as well as between crystalline and amorphous phases under external pressure. Herein, using first-principles density functional theory (DFT) and ab initio molecular dynamics (AIMD) calculations, we investigate the origin of the pressure-induced amorphization in CsPbI3. We find that the amorphous-like structures obtained from AIMD calculations become more stable than the orthorhombic Pbnm phase above 6.66 GPa, in good agreement with the experimental value (4.44 GPa). We further find that an imaginary flat band appears in the phonon dispersion of the orthorhombic CsPbI3 phase across the Brillouin zone at 10 GPa, leading to degenerate lattice instabilities. These energetically degenerate phonon modes are related to PbI6 octahedral tilting modes and provide random local distortions, leading to amorphization.
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